The ability of various solids to act as flame retardants and/or smoke suppressants is known in the art. Such solids act by various mechanisms to provide flame retardancy including the following:
a) Release of Water and/or Carbon Dioxide--Hydrated salts (such as magnesium sulfate pentahydrate, aluminum trihydrate, magnesium hydroxide, hydrated magnesium carbonate and so forth) decompose at high temperatures, and release water and or carbon dioxide in an endothermic reaction to quench a fire. PA1 b) Char Formation--When exposed to high temperatures, char formers, which include organic phosphates, zinc compounds, nitrogen compounds (such as melamine esters and polyamides) and metal borates, form char barriers which insulate the combustible materials from the fire. PA1 c) Free Radical Capture/Oxygen Deprivation--Halogen compounds alone or in combination with antimony will prevent combustion. The primary mechanism is believed to be the formation of a dense gas layer above the burning substance that inhibits or prevents oxygen from reaching the combustible material. There is also evidence in support of the ability of antimony halides to scavenge free radicals in the flame, stopping the reaction. PA1 d) Smoke Suppression--Smoke suppressants work by aiding the complete oxidation of carbonaceous materials formed in the flame and/or the formation of char or glasses. They are usually catalysts for oxidation reactions and/or char or glass formers. Typical smoke suppressants are molybdenum oxide and ferrocene or other metallocenes. PA1 (1) In wet media milling, smaller media are more efficient in producing finer particles within times of 10 minutes and less. PA1 (2) More dense media and higher tip speeds are desired to impart more energy to the particles being comminuted. PA1 (3) Lower fluid viscosities are beneficial in comminuting particles. PA1 (4) As the particles are reduced in diameter, exposed surface areas increase, and a dispersion agent is generally used to keep small particles from agglomerating. In some cases dilution alone can help achieve a particular ultimate particle size, but a dispersion agent is generally used to achieve long-term stability against agglomeration.
All of the above listed solids are used commercially to provide either flame retardancy or low smoke generation to plastics, carpets, fabrics, paper, paints, coatings, adhesives, wood composites and so forth. Unfortunately, the use of such solids often imparts other undesirable properties to the item to which they are added. Typical undesirable properties that result from adding solid particles of flame retardant or smoke suppressant compounds include: pigmentation (.e.g., addition of unwanted colors), opacity (e.g., loss of light transmission), stiffness (e.g., loss of hand in textiles), lowered impact strength (resulting, e.g., an increase in crack propagation), and setting of solids (in, e.g., paints, coatings and adhesives). Such undesirable properties can be reduced or eliminated by reducing average particle size and eliminating substantially all particles above about 1 micron.